Advances In Insect Control: The Role Of Transgenic Plants

Advances in Insect Control

Advances in Insect Control: The role of transgenic plants Edited by

NADINE CAROZZI AND MICHAEL KOZIEL

UK Taylor & Francis Ltd, 1 Gunpowder Square, London, EC4A 3DE USA Taylor & Francis Inc., 1900 Frost Road, Suite 101, Bristol, PA 19007 This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” Copyright © Taylor & Francis Ltd 1997 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwide, without the prior permission of the copyright owner. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN 0-203-21173-1 Master e-book ISBN

ISBN 0-203-26921-7 (Adobe eReader Format) ISBN 0-7484-0417-1 (Print Edition) Library of Congress Cataloging Publication data are available Cover design by Youngs Design in Production

Contents

Contributors Preface 1.

2.

xi xiv

Use of Transgenes to Increase Host Plant Resistance to Insects: Opportunities and Challenges

1

Introduction

1

The nature and magnitude of the insect pest problem

2

Natural host plant resistance

11

Transgenic approaches to host plant resistance

14

Requirements for success in creating and developing elite transgenic insect resistant cultivars

15

Resistance management

19

Registration studies for commercialization

20

Intellectual property

20

Status of transgenic crops in commercial development

21

Summary

22

References

22

Insect Control with Transgenic Plants Expressing Bacillus thuringiensis Crystal Proteins

25

Introduction

25

Bt crystal proteins

26

Structure-function relationship

30

Mechanism of action

31

Bt plants

35

Bt corn

39

v

3.

4.

5.

Bt resistance

40

Resistance management

42

Concluding remarks

45

References

45

The Development of a Comprehensive Resistance Management Plan for Potatoes Expressing the Cry3A Endotoxin

58

Introduction

58

Strategies to maximize the utility and durability of Colorado potato beetle resistant potatoes

59

Resistance management through integrated pest management

61

Education and communication

69

Strategies for the future

70

References

70

Acknowledgments

72

Transgenic Maize Expressing a Bacillus thuringiensis Insecticidal Protein for Control of European Corn Borer

73

Overview of crop damage from European corn borer

73

Transgenic maize for control of European corn borer

74

Engineering ( -endotoxins of Bacillus thuringiensis for expression in maize

75

Transformation of maize

76

Results of field trials with European corn borer resistant transgenic maize

76

Conversion and testing of transgenic maize lines for commercialization

79

Overview of registration process for European corn borer resistant maize hybrids

80

Resistance management

83

Summary

84

References

84

Enhancing Insect Resistance in Rice Through Biotechnology

87

Introduction

87

vi

6.

7.

8.

Insects and rice production

88

Rice biotechnology and insect resistance

88

Biotechnology and integrated pest management

93

Case study I: Rice gall midge

95

Case study II: Transgenic resistance to stem borers

99

Environmental and biosafety issues

102

Conclusion

103

References

104

Acknowledgments

108

Cholesterol Oxidase for the Control of Boll Weevil

109

New genes for insect control

109

Cholesterol oxidase—a new protein for insect control

112

Future directions

122

References

122

Acknowledgments

125

Vegetative Insecticidal Proteins: Novel Proteins for Control of Corn Pests

126

Introduction

126

Discovery and characterization of CRW-active VIPs

129

Discovery of Vip1A (a) and Vip2A (a) homologues

133

Discovery and characterization of BCW-active VIPs

134

Summary

136

References

137

Acknowledgments

140

Plant Lectins as Insect Control Proteins in Transgenic Plants

141

Introduction

141

Artificial diet bioassays

142

Lectins as insect control proteins

143

Artificial bioassay summary

148

vii

9.

10.

Transgenic plant bioassays

148

Mode of action

151

Insect resistance to lectins

153

Concerns regarding the utilization of lectins in transgenic plants

154

Future outlook

155

References

155

Transfer of Bruchid Resistance from the Common Bean to Other Starchy Grain Legumes by Genetic Engineering with the -Amylase Inhibitor Gene

159

Introduction

159

The bruchid life cycle

159

Seed defenses

160

Phytohemagglutinin, arcelin and -amylase inhibitor: Seed defense proteins of the common bean

162

Expression of PHA, arcelin and Al in developing bean seeds and seeds of transgenic tobacco plants

165

Al forms a small gene family in P. vulgaris, its wild accessions and closely related species in the genus Phaseolus

168

The molecular structure of Al and its binding to -amylase

169

Transfer of bruchid resistance from beans to peas by genetic engineering with the Al gene

171

Can beans be made resistant to New World bruchids with Al genes?

173

Will Al-containing legumes be safe to eat?

174

References

175

Acknowledgments

178

Proteinase Inhibitors and Resistance of Transgenic Plants to Insects

179

Introduction

179

Proteinase inhibitors

180

Three-dimensional structures and interactions of inhibitors with target enzymes

183

Proteinases of different classes as targets of inhibitors

183

viii

11.

12.

Insect digestive proteinases and protein digestion in phytophagous insects

186

Molecular genetics of insect digestive proteinases

190

In vitro inhibition of insect proteinases by proteinaceous inhibitors

191

Bioassays using proteinase inhibitors

194

Plants transformed with proteinase inhibitor genes

197

Summary and prospects

199

References

200

Acknowledgments

210

Chitinases for Insect Control

211

Introduction

211

Microbial chitinases for pest control

213

Plant chitinases for pest control

214

Insect chitinases for pest control

214

Expression and regulation of Manduca sexta chitinase

214

Transgenic plants expressing an insect chitinase

215

Baculovirus expressing M. sexta chitinase has enhanced larvicidal activity

216

N-acetylglucosaminidases for pest control

216

Concluding remarks

217

References

217

Acknowledgments

220

The Role of Peroxidase in Host Insect Defenses

221

Peroxidase properties

221

Peroxidase functions

223

Defensive function

225

Potential for producing insect resistance with transgenics expressing novel forms or levels of peroxidase

229

Insect resistance of transgenic plants expressing peroxidase

232

ix

General conclusions

238

Implications and further research needs

240

References

244

Acknowledgments

253

13. Insecticidal Compounds Induced by Regulated Overproduction of Cytokinins in Transgenic Plants

254

Introduction

254

Secondary metabolism and cytokinins

255

Endogenous modulation of cytokinin concentrations

256

Developmental effects in transgenic plants

257

Insect resistance

258

Cytokinin-induced insecticidal compound(s)

259

Specificity of insecticidal compound(s)

261

Future perspectives

262

References

263

14. Genetic Engineering of Plant Secondary Metabolism for Insect Protection

267

Nicotine

268

Cyanogenic glucosides and glucosinolates

272

Cyclic hydroxamic acids (DIBOA and DIMBOA)

279

Pyrethrin

284

Rotenone

288

Unsaturated amides

290

References

294

15. Managing Resistance to Transgenic Crops 5. Introduction

304 304

Potential for resistance to transgenic plants

305

Principles of selection for resistance

306

Resistance management tactics for transgenic crops

313

x

Integrated pest management

323

Conclusions

325

References

327

Acknowledgments

330

Index

331

Contributors

James E.Baker US Grain Marketing Research Laboratory, Grain Marketing and Production Research Center, USDA-ARS, Manhattan, Kansas, 66502 Craig A.Behnke Department of Biochemistry, Kansas State University, Manhattan, Kansas, 66506 John Bennett Division of Plant Breeding, Genetics and Biochemistry, International Rice Research Institute, PO Box 933, 1099 Manila, Philippines George Buta Horticultural Crops Quality Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland, 20705 Nadine B.Carozzi Ciba-Geigy Corporation, Agricultural Research Unit, Research Triangle Park, North Carolina, 27709 Scott Chilton Department of Botany, North Carolina State University, Raleigh, North Carolina, 27695 Maarten J.Chrispeels Department of Biology, University of California at San Diego, 9500 Gilman Drive, La Jolla, California, 92093–0116 Michael B.Cohen Entomology and Plant Pathology Division, International Rice Research Institute, PO Box 933, 1099 Manila, Philippines Thomas H.Czapla Pioneer Hi-Bred International, Johnston, Iowa, 50131 Patrick F.Dowd US Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, 1815 N. University Street, Peoria, Illinois, 61604 Nicholas Duck Ciba-Geigy Corporation, Agricultural Research Unit, Research Triangle Park, North Carolina, 27709 Stephen Evola Ciba-Geigy Corporation, Agricultural Research Unit, Research Triangle Park, North Carolina, 27709

xii

Jeffrey A.Fabrick Department of Biochemistry, Kansas State University, Manhattan, Kansas, 66506 Jennifer Feldman NatureMark Potatoes, 300 East Mallard Drive, Boise, Idaho, 83706 Benhzad Ghareyazie Division of Plant Breeding, Genetics and Biochemistry, International Rice Research Institute, PO Box 933, 1099 Manila, Philippines Sunggi Heu Plant Molecular Biology Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland, 20705 Lowell Johnson Department of Plant Pathology, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, Kansas, 66506 Michael R.Kanost Department of Biochemistry, Kansas State University, Manhattan, Kansas, 66506 Sanjay K.Katiyar Division of Plant Breeding, Genetics and Biochemistry, International Rice Research Institute, PO Box 933, 1099 Manila, Philippines Gurdev S.Khush Division of Plant Breeding, Genetics and Biochemistry, International Rice Research Institute, PO Box 933, 1099 Manila, Philippines Michael G.Koziel Ciba-Geigy Corporation, Agricultural Research Unit, Research Triangle Park, North Carolina, 27709 Karl J.Kramer US Grain Marketing Research Laboratory, Grain Marketing and Production Research Center, US Department of Agriculture-ARS, Manhattan, Kansas, 66502 L.Mark Lagrimini Department of Horticulture and Crop Science, The Ohio State University, 2001 Fyffe Court, Columbus, Ohio, 43210 Iris McCanna Plant Molecular Biology Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland, 20705 Subbaratnam Muthukrishnan Department of Biochemistry, Kansas State University, Manhattan, Kansas, 66506 Marnix Peferoen Plant Genetic Systems, N.V., Jozef Plateaustraat 22,9000 Ghent, Belgium John P.Purcell Monsanto-GG4G, 700 Chesterfield Village Parkway North, St Louis, Missouri, 63198 Gerald R.Reeck Department of Biochemistry, Kansas State University, Manhattan, Kansas, 66506 Rick Roush Department of Crop Protection, Waite Campus, University of Adelaide, Glen Osmond, South Australia 5064, Australia

xiii

Ann Smigocki Plant Molecular Biology Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland, 20705 Terry Stone Monsanto Co., 700 Chesterfield Parkway North, St Louis, Missouri, 63198 Gregory W.Warren Ciba-Geigy Corporation, Agricultural Research Unit, Research Triangle Park, North Carolina, 27709 Frank White Department of Plant Pathology, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, Kansas, 66506 Chris Wozniak Northern Crop Science Laboratory, Agricultural Research Service, Fargo, North Dakota

Preface

This year will be remembered for the commercial introduction of three crops which are engineered for insect resistance, thereby marking the beginning of a new era in agriculture for the control of insect pests. Plant genetic engineering has moved in the past decade from the laboratory to the market-place as a new and powerful technology to provide both farmers and consumers with improved crops. This technology has the capability to impact agricultural practices more radically than any other single change in the past several thousand years of agriculture. Engineering plants for increased insect and disease resistance will improve both crop quality and yield. Eventually plants will be altered to withstand environmental stress, enhance their nutritional qualities, and be used to produce new and useful proteins. Engineering plants to resist insects is one of the most urgent demands of plant genetic engineering. Insect pests create very costly losses for farmers and attempts to mitigate insect damage usually require applications of chemical pesticides or sprayon biological pesticides. Insecticidal applications need to be properly timed to coincide with insect infestations and do not always reach burrowing insects. The introduction of plants with built-in resistance to various insect pests will have a tremendous impact on current agricultural practices. Now 1996–97 brings the first market introduction of genetically engineered commercially available insect tolerant corn, potato, and cotton plants expressing a Bacillus thuringiensis endotoxin gene. These genetically engineered plants provide resistance against some of the worst crop pests. The first generation of products are still new, but many innovations are visible on the horizon. This book attempts to examine today’s technology and successes and to also look at candidates for the next generation of insect control for transgenic crops. The reality of plant genetic engineering is that although the promise is great, the steps involved in implementing useful technologies are tedious and often fraught with technical difficulties that underscore our ignorance of the workings of various biological processes. Although transformation of tobacco was first reported in 1983, it was still a large hurdle to develop technologies to reproducibly and efficiently introduce new genes into major commercial crops. The use of genetically engineered plants to combat losses caused by insects

xv

requires an understanding of not only the crop but an understanding of the equally complex and often less studied insect pest. Plants and insects both hold many mysteries than we have not yet begun to understand. Novel insecticidal proteins described in this book may bring new and different challenges that will no doubt be specific for each crop and insect combination. Novel approaches to introduce multi-gene pathways and/or regulation of existing plant genes will present even more challenges. But while this is a hurdle for the development of commercial varieties, it is the great appeal and challenge for the scientists in this area. It provides an opportunity to contribute to the well being of mankind while unraveling a few of the mysteries of nature. While agricultural biotechnology is still in its infancy, its promise is bright. It is immensely rewarding to be a contributor and witness to this new day. We hope that this book serves as a rich source of information about both the current status of genetically engineered insect resistant crops that have been recently commercialized to the many new advances and prospects for the future of engineering insect resistant crops. Dedicated to our children who will enjoy a better world. Nadine Carozzi and Mike Koziel

1 Use of Transgenes to Increase Host Plant Resistance to Insects: Opportunities and Challenges NICHOLAS DUCK and STEPHEN EVOLA

Introduction Most plant species experience insect predation, although the severity and economic importance of that predation varies significantly among crop species. In the manmade environments of agricultural crop production for food or fiber this predation is almost always to the detriment of the output of the agricultural system yield. In fact, the development of genetic monocultures managed with intensive inputs of nutrients and, in many cases, water, to produce luxuriant growth of a limited number of genotypes per crop, has altered the co-evolutionary balance among crop species and their insect predators and increased the potential for epizootics. To increase and/or stabilize crop yields two primary approaches have been used to decrease insect predation. The first is the development and application of ‘sprayons’, be they synthetic or natural chemicals, microbial fermentation products or living macro-organisms. The second approach is development of crop varieties with increased host plant resistance based on genetic factors found within the crop species or in closely related wild species. Today the development of genetic engineering technology has enabled the introduction of genetic material from any species into major crop plants. Genes encoding insect resistance have been introduced in several major crop species, producing dramatically enhanced insect resistance compared to what had been obtainable by conventional breeding. This book provides many excellent examples of insect controlling principles from a variety of sources and their successful introduction into the genomes of plants, many of which are important crop plants. Some of these principles have reached the marketplace in elite varieties and hybrids with superior agronomic performance. Others are still in the proof-of-concept phase. The creation of higher levels of insect resistance in transgenic crop plants is not without considerable technical challenges. The first step involves the time consuming process of identification and isolation of insect controlling principles, and the genes that encode them. A critical requirement for these principles is that they possess a sufficiently high specific activity to achieve effective control of

2 ADVANCES IN INSECT CONTROL

insect pests, given the biosynthetic capacities of the host plant and the need to maintain established levels of agronomic performance. Overproduction of certain active principles with low specific activities may disrupt developmental processes and diminish final crop yields. Other insecticidal proteins with high specific activities may not be amenable to production in transgenic plants if they disrupt critical plant physiological processes. Technical solutions involving cellular sequestration of the protein and tissue specific expression may be required. Solutions such as these may add several years to the production of commercially acceptable products. The second but equally important step is the development of transformation systems, particularly with elite genotypes, that permit the stable heritable insertion of foreign DNA. Next the development of breeding and/ or evaluation methods must be established to permit the introduction of a desirable transformation event into other lines or varieties and insure that any given transgenic line is unaltered in performance relative to its non-transgenic counterpart. Field trial methods need to be developed to demonstrate convincingly the enhanced resistance of the transgenic plants. In addition, there are challenges that need to be met in the areas of regulatory affairs, production and quality control, resistance management and, for a commercial cultivar, intellectual property. Finally, the transgenic insect resistant crop has to meet with both grower and public approval and acceptance. As the examples in this book demonstrate, the challenges can be met and the benefits of greatly enhanced host plant resistance to insects through genetic engineering are obvious, great and unique. The Nature and Magnitude of the Insect Pest Problem Insect Pests of Major Crops The major crops (‘major’ defined as harvested mass of at least 20 million metric tons per year) of the world and their most important insect pests are shown in Table 1.1. Although several insect pests can be determined to be significant pests for a given crop, crops vary considerably in the extent to which insecticides are normally used Table 1.1 Major crops and their chief insect pests Crop (in order by planted hectares, worldwide)

World production (in million metric tons)1

Major insect pests2,3,4

Wheat (Triticum aestivum)

551

Aphids (Rhopalosiphum padi, Schizaphis graminum, Sitobion avenue) Senn pest (Eurygaster integriceps)

TRANSGENES INCREASE HOST PLANT RESISTANCE 3

Crop (in order by planted hectares, worldwide)

Rice (Oryza sativa)

World production (in million metric tons)1

520

Major insect pests2,3,4 Hessian fly (Mayetiola destructor) Wheat bulb fly (Delia coarctata) Brown planthopper (Nilaparvata lugens) Green planthopper (Nephotettix virescens) Yellow rice borer (Tryporyza incertulas) Striped rice borer (Chilo suppressalis) Gall midge (Orseolia oryzae)

Table 1.1—Continued Crop (in order by planted hectares, worldwide)

World production (in million metric tons)1

Major insect pests2,3,4

Maize (Zea mays)

479

Potato (Solanum tuberosum)

261

European corn borer (Ostrinia nubilalis) Asian corn borer (Ostrinia furnacalis) Other stem and stalk borers (Chilo and Sesamia spp., Busseola fusca) Southwestern corn borer (Diatrea grandiosella) Corn rootworms (Diabrotica virgifera virgifera, D. longicornis barberi, D. undecimpunctata) Black cutworm (Agrotis ipsilon) Fall armyworm (Spodoptera frugiperda) Corn earworm (Helicoverpa zed) Sugar cane borer (Diatrea saccharalis) Lesser corn stalk borer (Elasmopalpus lignosellus) Colorado potato beetle (Leptinotarsa decemlineata)

4 ADVANCES IN INSECT CONTROL

Crop (in order by planted hectares, worldwide)

World production (in million metric tons)1

Cotton (Gossypium hirsutum)

21 (lint) 38 (meal)

Soybean (Glycine max)

103

Major insect pests2,3,4 Potato leafhopper (Empoasca fabae) Potato tuber moth (Phthorimaea operculella) Aphids (Aulacorthum solani, Myzus persicae) Wireworms (Agriotes spp.) Black blister beetles (Epicauta spp.) Bollworm (Helicoverpa zea) Tobacco budworm (Heliothis virescens) American budworm (Heliothis armigera) Cotton boll weevil (Anthonomus grandis) Pink bollworm (Pectinophora gossypiella) Jassids (Empoasca spp.) Cotton leafhopper (Pseudatomoscelis seriatus) Plantbugs (Lygus lineolaris, L. hesperus) Green cloverworm (Plathypena scabra) Soybean looper (Pseudoplusia includens) Velvetbean caterpillar (Anticarsia gemmatalis) Mexican bean beetle (Epilachna varivestis) Bean leaf beetle (Cerotoma trifurcata) Thrips (Sericothrips variabilis) Potato leafhopper (Empoasca fabae) Corn earworm (Helicoverpa zea) Green stink bug (Acrosternum hilare) Threecornered alfalfa hopper (Spissistilus festinus) Lesser corn stalk borer (Elasmopalpus lignosellus)

TRANSGENES INCREASE HOST PLANT RESISTANCE 5

Table 1.1—Continued Crop (in order by planted hectares, worldwide)

World production (in million metric tons)1

Major insect pests2,3,4

Sunflower (Helianthus annuus)

23

Rape (Brassica napus)

20

Sugar beet (Beta vulgaris)

38 (total raw sugar)

Sugar cane (Saccharum interspecific hybrids) Grapes (Vitis vinifera)

98 (total raw sugar)

Tomato (Lycopersicon esculentum)

69

Blue bugs (Calidea spp.) Green stink bug (Nezara viridula) American bollworm (Heliothis armigera) Chafer grubs (Schizonycha spp.) Cabbage aphid (Brevicoryne brassicae) Brassica pod midge (Dasyneura brassicae) Red turnip beetle (Entomoscelis americana) Blossom beetles (Meligethes spp.) Flea beetles (Phyllotreta spp., Psylliodes chrysocephala) Cabbage seed weevil (Ceutorhynchus assimilis) Cabbage stem weevil (Ceutorhynchus quadridens) Beet leafhopper (Circulifer tennellus) Black bean aphid (Aphis fabae) Peach-potato aphid (Myzus persicae) Mangold fly (Pegomyia betae) Silver-Y moth (Autographa gamma) Sugar cane borer (Diatrea saccharalis) Grape leafhoppers (Erythroneura spp.) Grape phylloxera (Viteus vitifolii) Root mealybugs (Planococcus spp.) Grape mealybug (Pseudococcus maritimus) Tobacco whitefly (Bemisia tabaci)

57

6 ADVANCES IN INSECT CONTROL

Crop (in order by planted hectares, worldwide)

World production (in million metric tons)1

Coconut (Cocos nucifera) Yam (Dioscorea spp.)

42 24

Cassava (Manihot esculenta)

154

Major insect pests2,3,4 Glasshouse whitefly (Trialeurodes vaporariorum) Green stink bug (Nezara viridula) Tomato leafminer (Scrobipalpula absoluta) Tomato fruitworms (Heliothis spp.) Onion thrips (Thrips tabaci) No major insects Sweet potato weevil (Cylas spp.) Thrips (Frankliniella williamsii, Corynothrips stenopterus, Caliothrips masculinus) Cassava hornworm (Erinnyis ello) Whiteflies (Bemisia tabaci, Aleurotrachelus spp.) Mealybugs (Phenaococcus gossypii, Pseudococcus spp.) Scales (Aonidomytilus albus)

Table 1.1—Continued Crop (in order by planted hectares, worldwide)

World production (in million metric tons)1

Major insect pests2,3,4

Sweet potato (Ipomoea batatas) Sorghum (Sorghum bicolor)

126

Millet (several spp.)

29

Oats (Avena sativa)

34

Sweet potato weevil (Cylas spp.) Sorghum midge (Contarinia sorghicola) Shoot fly (Atherigona soccata) Stem borer (Chilo partellus) Greenbug (Schizaphis guaminum) Millet grain midge (Geromyia pennisiti) Wheat aphid (Schizaphis graminum)

58

TRANSGENES INCREASE HOST PLANT RESISTANCE 7

Crop (in order by planted hectares, worldwide)

Rye (Secale cereale)

World production (in million metric tons)1

Major insect pests2,3,4 Grain aphid (Sitobium avenue) Bird-cherry aphid (Rhopalosiphum padi) Frit fly (Oscinella frit) Cereal leaf beetle (Oulema melamopa) Bird-cherry aphid (Rhopalosiphum padi) Wheat aphid (Schizaphis graminum) Grain aphid (Sitobium avenae) Frit fly (Oscinella frit)

27

1

FAO (1991) Hill (1987) 3 Dicke and Guthrie (1988) 4 Niles (1980) 2

(see Table 1.2). In terms of total insecticides used and proportion of acres treated, cotton, maize and potatoes have the largest commercially important insect problems. Value of Insect Resistance in Major Crops Estimated Through Crop Losses Total yield losses from all causes to all crops are roughly estimated to be $500 billion (US) per year (Oerke et al., 1994). Pimentel (1991) estimates the sum of preTable 1.2 Insecticide use on selected crops (Palm, 1991) Crop Non-food Cotton Food Maize Rice Wheat Soybeans Potatoes All crops

Acres treated %

Amount (% of total used on all crops)

61

47

35 35 7 8 77 6

17 1 1 4 2 35 (% of total pesticides)

8 ADVANCES IN INSECT CONTROL

harvest and postharvest losses to pests (weeds, pathogens and insects) is about 45% (25–35% preharvest, 10–20% postharvest) worldwide. In the US, preharvest losses are estimated to be about 37% and postharvest losses 9%. Of the preharvest losses in the US, approximately 13% result from insect predators. Losses are large and ubiquitous and chemical controls are not fully effective. Yield losses in selected crops, with and without control measures, caused by specific arthropod pests are shown in Table 1.3. Yield losses vary by crop (see Table 1.4). Worldwide 15.6% of the total production, valued at $90.5 billion (US), of the eight principal food and cash crops (coffee, potato, soybean, maize, barley, cotton, rice, and wheat), was lost to animal predators, primarily insects, in 1988–90. These losses are sustained even though control measures, chiefly insecticide applications, are used on a high proportion of Table 1.3 Worldwide yield losses resulting from specific anthropod pests Calculated yield loss (%) Crop

Pest

Without control

With control

Barley Sugar beet Maize

Green bug Root maggot Cornfield ant Corn rootworms Garden symphalid Leafhoppers Southwestern corn borer White grubs Wireworms Aphids Boll weevil Cabbage looper Cotton aphid Cotton flea hopper Heliothis spp. Pink bollworms Thrips Aphids Armyworms Colorado potato beetle European corn borer Flea beetles Green peach aphid Leafhoppers

84 23 20 16 14 75 34 43 48 22 31 35 5 39 91 36 68 15 59 47 54 43 4 36

7 8 3 5 7 38 10 11 18